Process of treating concrete



Sept. 12, 1933.

a: HOFFMANN 1,926,623

PROCESS OF TREATING CONCRETE Filed March l9, 1928 gwuentw attotvwlag Patented Sept. 12, 1933 PATENT rrie PROCESS OF TREATING CONCRETE Edward A. Hofl'inann, Reading, Pa,

(Hinton Motors Corporation,

assignor to Reading, Pa, a

corporation of New York Application March'lil, 1928. Serial No. 262,789

8 Claims. (Cl. 83--73) My invention consists in an improved process of treating concrete the main object of which is to enable the supplying thereof in thoroughly mixed and unaerated condition for deferred. use, as after transportation to a greater or less distance from a stationary primary mixing plant; and which is fully described in connection with diagrammatic illustrations showing elementary means practically employed therefor, and clearly defined in the subjoined claims.

In the mixing of concrete ingredients as commonly eiiected, the mass has been subjected to a high degree of agitation, as by means of battles stirrers or like means provided in a rotary container and adapted to throw the material about therein so as to forcefully produce a thorough mixing.

I have found by extensive experimenting, that such commonly employed agitative method of 2G mixing the concrete ingredienta, brings about somewhat of a churning action which tends to entrain more or less air, evidenced by bubbles and foaming of the aqueous mixture and with consequent more or less imperfect hydration and bonding of the ingredients and a "resulting sponginess in the plastic compound; and more particularly, that deferred use of such mixtureas by transportation thereof to a place of use more or less distant from the stationary mixing plant which it is very frequently desirable to employ, results either in separation of the ingredients "by force of gravity when such agitative action is suspended, or,'if the latter is continued, in an objectionable stifiening of the mixture promoted by long continued working-out of the aqueous content into the air space of the contamer: So that in either case the concrete is apt to be in improper condition for such deferred use.

In endeavoring to overc'ne these difficulties, particularly as to the supplying of concrete rrimarily mixed in stationary plants, for deferred use at a distance from the latter, I have found it essential to the insuring of proper conditioning of the concrete, first that the ingredients be maintained in a state of motion adapted to prevent any gravitating separation; and second that such motion be effected without aerating or stifiening effect upon the mixture, by maintaining throughout the latter a slow circulating movement thereof with relative movement of the ingredients but without substantial breaking of the air-exposed surface of the mixture; I have discovered that by this means, I am able to extract nearly all air which has been entrained in the mixture by the usual agitative methods above referred to. And I have found further that my improved process of so treating concrete can be effected by proper operation of simple and elementary apparatus, as fully set forth with referto ence to the accompanying diagrammatic drawing; and that desired actual results heretofore considered unattainable are secured.

Fig. 1 is a cross-sectional view of a rotary container in a state of rest, showing a concrete charge or batch in excess of one half the capacity of the container so that the normal level thereof is above the longitudinal axis. Fig. 2 is a similar view indicating the circulating flow of the ingredients in a vertical cross-sectional plane'of the container, when the latter is slowly rotated in the direction of the arrow to carry out my improved process. Figs. 3 and 4 are reduced diagrammatic elevations showing containers of plain and'tapered cylindrical form respectively.

The charge or batch of concrete indicated as partially filling the container 6, may have been primarily mixed by usual agitation means re ferred to, and the container together with suitable rotating mechanism thereformay be mount-- ed upon a truck by means of which its contents are conveyable to a more or less distant place of use if desired; the batch consisting of stone, sand, cement and water in desired proportions, as usual-and my invention relating wholly to the improved treating process effected in the elementary rotary container indicated.

This cylindrical container 6 is indicated as of circular cross-section at all points of its length, with smooth inner walls affording no obstruction other than frictional contact therewith, to the movement of the contained material. In being used to carry out my improved process this container is simply rotated uniformly at slow speed so as to produce a circulating fiow'of the 5 contained material in a vertical plane, .as diagrammatically indicated. The charge may be introduced through a suitable opening 7 having a sealing closure 8, andissimilarly discharged for use; the particular construction employed being immaterial to my invention.

When the container is slowly rotated in the direction of the arrow, as indicated in Fig. 2, the material in frictional contact with the rising portion of the Wallis carried upward somewhat above the normal stationary level indicated in Fig. 1, until it falls away from the overhanging curve of the wall with a gentle rolling-over motion as indicated diagrammatically at 10 Fig. 2; while the material in frictional contact with the opposite descending portion of the wall, is carried downward to below said normal level, with a resulting rollingover motion of the: adjacent surface material as indicated at 11; these gentle rolling-over motions changing the relative positioning of the contacting ingredients without however breaking up the continuous exposed surface or the batch as would be done by the more or less violent agitation incident to employment of stirringor deflecting devices for forcible mix This opposite rolling-over motion of the respectively raised and lowered surface material, produces a corresponding flow throughout the mass in every vertical plane, so as to very simply carry into practical effect the stated essential steps of my improved process; namely the maintaining of the ingredients in a state of motion which insures their proper mixture without gravitating separation, and with retention and proper distribution of the hydrating constituent. ,While this rolling-over motion is going on with its incidental circulatory travel of the mixture, the air bubbles in the mixture will be carried alon until they reach the inclined continuous surface of the mixture, there to combine with the air above the mixture, or to be carried along to the lowered end of this surface to accumulate and gradually break when contacting with each other.

In the actual employment of my improved process I have found that it may be very satisfactorily carried out by charging the container to any extent in excess oi one half its capacity, which charging brings the normal level above the axis, but I preferably charge between twothirds and three-fourths of the container capacity. g

The speed of rotation may be varied to accord with the charge and the cross-sectional diameters of the container, but with due regard for secur-. ing the easy rolling-over action of the material, as I have termed it, whereby the desired flow is attained without breaking up of the continuous surface of the batch.

In Fig. 2 l. have indicated the apparent flow lines of the mixture in diametral plane, as caused by the described rolling-over action of the material at the raising and falling surfaces thereof respectively, and by the lower position 2 of thecentre of gravity of the mixture relative to the axis of rotation 1; whereby the whole mass is given a circulatory flow, as indicated by the arrows, without breaking up of the air-exposed surface.

The effects of maintaining such a slow circulatory movement of the entire mass ofmixed ingredients with maintenance of an unbroken exposed surface are: First, the securing of more uniform hydration and mixing of the ingredients, without gravitatiug separation thereof, or escape of the hydrating element therefrom with resulting stiffening oi the mixture; and second the prevention of the highly objectionable spongy characteristic incident to incorporation of air in the mixture, by giving up air within the mixture, in formof bubbles, to the otherwise unoc cupied space in thecontainer.

As 'amatter of fact it has been found, by "compression tes made by the testing laboratories of Columbia University Department of Civil Engineering, that numerous specimens of various mixtures .1 of concrete treated by my improved process,-for deferred use varying from four minutes to two hours and thirty minutes, showed an increasins compression strength with lonq' [continuance of my treatment, apparently indicating the resultant expulsion of air entrained in the primary mixing, as well as superior hydration.

In employing a container cylinder of uniform diameter throughout the indicated flow of maaifected by the vertical-end-wall contacts there of; and such indicated circulatory how will be substantially maintained in the tapered form of cylinder indicated in Fig. 4, though in the latter case the diametral paths will be noticeably inclined to the axis of rotation by an endwise spiral movement of the contained mass due to the different frictional effect of the two end walls. Such slow endwise movement 02 the mass in connectlon with the flow indicated in the diametral planes, tends to more. thoroughly mix the ingredients without breaking the air-exposed surface. The carryirm out of my improved process may obviously be modified within the spirit of my invention as defined in the claims. Furthermore, while I refer to the process as being particularly suitable for conditioning concrete, the same is intended to epply'to any form of cementitious material or its equivalent, and'the term concrete" should be so interpreted.

What I claim is:

l. The process of preparing concrete mixtures for deferred use comprising the stepsof mixing all ingredients at a central station to form concrete, transporting the mixture to a remote point and conditioning the mixture during transportation by subjecting the same to a combined slow, rolling and flowing motion while maintaining an unbroken surface on the entire exterior of the mixture for the expulsion of entrained air therefrom. Q

2. The process of preparing concrete mixtures for deferred use comprising the steps of mixing all ingredients at a central station to form concrete, partly filling a. container with said mixture, transporting the container to a remote point and conditioning said mixture during transportation by subjecting the same to a combined slow, rolling and flowing motion while maintaining an unbroken surface on the entire exterior of the mixture.

3. The process of preparing concrete mixtures 'terial in the diametral planes is not materially for deferred use comprising the steps of mixing all ingredients at a central station to form concrete, transporting the mixture to a remote point and conditioning the mixture by subjecting the same during transportation to circulatory motion while maintaining an unbroken surface on the entire exterior of the mixture.

4'. The process of preparing concrete mixtures comprising the steps of mixing all ingredients into a mass of uniform consistency to form concrete, and conditioning said mass by maintaining throughoutisaid mass a slow circulatory movement and maintaining an unbroken air exposed surface for the expulsion of entrained air therefro 5 fThe process of preparing concrete mixtures for deferred use comprising the steps of mixing all mgredlentsthereof into a mass of uniform consistency at a central station, transporting said mass to a remote point, and conditioning said mass during transportation by maintaining throughout said mass a slow clrculatory movement and maintaining an unbroken air exposed surface.

6. The process of preparing concrete mixtures comprising the steps of mixing all ingredients into a mass 01' uniform-consistency to for-moon- H ccy at a. ten tion. lntrodu the resultin: into a, cylinder mounted for rotatlon on a v horizontal ads and havin; a hollow unobstructed interior, then transporting the cylinder to the desired destination and rotating the cylinder constantly during such transportation to preclude stratifying or solidbflcstion of the contents thereo! solely through rotation, of the cylinder. and to uce a rolling over motion oi. the Q v EDWARD A. v

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